ch 17 - translation

Question 1

translation

Answer 1

process where the cell interprets a genetic message and builds a polypeptide

Question 2

how is a genetic message transferred to ribosome

Answer 2

cell translates mRNA message into a protein
tRNA brings correct amino acid based on anticodon-codon matchup

Question 3

tRNA makeup , similarities differences

Answer 3

molecules of tRNA are not all identical
each carries a specific amino acid on one end
each has an anticodon on the other end
consists of a single RNA strand about 80 nucleotides long
twists and folds into three-dimensional molecule with hydrogen bonds

Question 4

in order to ensure that tRNA has the correct amino acid, what is necessary

Answer 4

aminoacyl-tRNA
^ has active site that tRNA will bind to via anticodon portion, and amino acid will bind to enzyme at another active site, only if the tRNA bound to it has a specific anticodon
uses ATP to bond amino acid to tRNA

Question 5

steps of accurate translation

Answer 5

1.a correct match between a tRNA and an amino acid, done by the enzyme aminoacyl-tRNA synthetase
2. a correct match between the tRNA anticodon and an mRNA codon

Question 6

why do we need 20 different synthetases if they all do the same thing

Answer 6

we have 20 different amino acids each with unique R-groups
active sites need to be complementary to the R-groups

Question 7

the ribosome role

Answer 7

part of the cellular machinery for translation
facilitates the specific coupling of tRNA anticodons with mRNA codons during protein synthesis

Question 8

the ribosome structure

Answer 8

made of large and small subunit
subunits composed of proteins and ribosomal RNA
ribosome subunits are constructed in nucleolus in eukaryotes
subunits join to form a functional ribosome only when they attach to an mRNA molecule

Question 9

ribosome binding sites

Answer 9

three bindings sites for tRNA
A site
P site
E site
mRNA binding site

Question 10

A site - ribosome

Answer 10

carries the next amino acid to be added to the chain
very right
tRNA enters in A site

Question 11

P site

Answer 11

holds the tRNA that carries the growing polypeptide chain
middle site
holds strand of amino acid thats growing

Question 12

E site

Answer 12

discharged tRNAs leave

Question 13

give basic steps of tRNA in ribosomes

Answer 13

tRNA enters ribosome in A site with amino acid attached to it
this amino acid will join the polypeptide chain in the P site if the correct tRNA joined the ribosome (anticodon and codon match up)
tRNA that donated amino acid then leaves the ribosome in E site

Question 14

three stages of translation

Answer 14

initiation
elongation
termination

Question 15

initiation - translation

Answer 15

bring together mRNA, a initiator tRNA, and two ribosomal units
a small ribosomal subunit binds with mRNA and a tRNA
the small subunit moves along mRNA until it reaches the start codon (AUG)
proteins called initiation factors bring in the large subunit and position so the initiator tRNA occupies p-site
energy is gtp

Question 16

direction of polypeptide

Answer 16

new amino acids are joined to carboxyl groups (amine to carboxyl) creating peptide bond

Question 17

elongation

Answer 17

amino acids are added one by one to preceding amino acid
three steps:
1.codon recognition
2.peptide bond formation
3.translocation

Question 18

codon recognition (first step of elongation)

Answer 18

tRNA enters A site and hydrogen bonds will form between mRNA codon at A site and anticodon on tRNA that carries correct amino acid

Question 19

peptide bond formation

Answer 19

rRNA catalyzes bond between polypeptide in P site and new amino acid in A site
separate tRNA at P site from growing chain

Question 20

translocation

Answer 20

ribosome moves tRNA with attached chain of AA and mRNa from A to P site and P to E site for release

Question 21

termination of translation

Answer 21

occurs when a stop codon reaches the A site of the ribosome
when stop codon in A site causes the A site to accept a protein called a release factor
the release factor causes the additionof a water molecule instead of an amino acid
reaction releases the polypeptide ad the translation assembly comes apart

Question 22

polyribosome

Answer 22

formed when a number of ribosomes are translating a single mRNA simultaneously
allows more protein to be made more efficiently

Question 23

two populations of ribosomes in cells

Answer 23

free ribosomes
bound ribosomes

Question 24

free ribosomes

Answer 24

in the cytosol
mostly synthesize proteins that function in the cytosol

Question 25

bound ribosomes

Answer 25

attached to ER
make proteins of the endomembrane system and proteins that are secreted from the cell